1. Field of the Invention
The present invention relates to an ink jet recording apparatus that circulates an ink and ejects the ink from an ink jet head and an ink supplying mechanism and an ink supplying method for supplying the ink in the ink jet recording apparatus.
2. Description of the Related Art
A technique for ejecting an ink from a nozzle of an ink jet head while circulating the ink in an ink jet recording apparatus is disclosed in, for example, JP-T-2002-533247 (the term “JP-T” as used herein means a published Japanese translation of a PCT patent application) or US 2002/0118256A1. In such an ink jet recording apparatus, a liquid surface of an upstream side tank is kept constant. An ink in the upstream side tank flows into a printing head through an upstream side channel of the printing head and flows into a downstream side tank through the printing head and through a downstream side channel. A liquid surface of the downstream side tank is kept constant. A circulating pump is provided in a circulation path. The circulating pump pumps up the ink from the downstream side tank, cause the ink to pass a filter, and pumps up the ink to the upstream side tank through a feedback channel. The circulating pump has a function of directly coming into contact with the ink and feeding the ink to circulate along a predetermined circulation path. Therefore, for example, the circulating pump is required to keep chemical stability against the ink, not to cause dust, and to less easily cause foaming. However, it is extremely difficult to realize a pump that satisfies these requirements and has high reliability and durability.